Rett described the syndrome in 1966 in young girls in Vienna. Although there is a classical clinical picture, it is now evident that variant forms and affected males occur.



(1) The original syndrome was thought to occur exclusively in females. The Rett Syndrome Diagnostic Criteria Work Group did not include this as a necessary criteria so as not to bias the diagnosis and miss the rare case in males.

(2) After these criteria were defined, the molecular basis (mutation in the MECP2 gene, which encodes a methyl CpG binding protein) was identified.

(3) In the variant forms of the disease some patients may be severely affected while others are mildly affected.

(4) While initially thought to be rare, it is now recognized as occurring much more frequently. The availability of genetic testing will probably increase its recognition.


Necessary criteria:

(1) apparently normal prenatal and perinatal period

(2) apparently normal psychomotor development through the first 6 months (and possibly up to the age of 18 months)

(3) normal head circumference at birth

(4) deceleration of head growth between 5 months and 4 years of age

(5) loss of acquired purposeful hand skills between 6 and 30 months of age, temporally associated with communication dysfunction and social withdrawal

(6) development of severely impaired expressive and receptive language, and presence of apparent severe psychomotor retardation

(7) stereotypic hand movements (hand wringing, hand squeezing, hand clapping-tapping, mouthing, "washing"/rubbing automatisms) appearing after purposeful hand skills are lost

(8) appearance of gait apraxia and truncal apraxia/ataxia between ages 1 and 4 years

(9) diagnosis tentative until age 2 to 5 years


Supportive criteria:

(1) breathing dysfunction (periodic apnea during wakefulness, intermittent ventilation, breath-holding spells, forced expulsion of air or saliva)

(2) EEG abnormalities (slow waking background and intermittent rhythmical slowing at 3-5 Hz; epileptiform discharges)

(3) seizures

(4) spasticity, often with associated development of muscle wasting and dystonia

(5) peripheral vasomotor disturbances

(6) scoliosis

(7) growth retardation

(8) hypotrophic small feet

(9) female gender


Exclusion criteria:

(1) evidence of intrauterine growth retardation

(2) organomegaly or other signs of storage disease

(3) retinopathy or optic atrophy

(4) microcephaly at birth

(5) evidence of perinatally acquired brain damage

(6) existence of identifiable metabolic or other progressive neurologic disorder

(7) acquired neurological disorders resulting from severe infection or head trauma


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